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Dehydration of Alcohols

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Presentation on theme: "Dehydration of Alcohols"— Presentation transcript:

1 Dehydration of Alcohols

2 Elimination Reactions
Y C - C X To make C=C need to eliminate X, Y.

3 3 ways to break 2 bonds 1. Concerted (x and y leave same time)
C - C X 3 ways to break 2 bonds 1. Concerted (x and y leave same time) 2. X leaves first 3. Y leaves first

4 Leaving Group

5

6

7 E1 Reaction R-X R X- Alkene + H+

8 E1 1 bond at a time Elimination

9 R+ SN1 E1 Rearrangement Substitution Elimination

10 SN1 E1

11 Dehydrohalogenation X C - C H Strong base

12 C-D bond stronger than C-H bond.
What is the mechanism of dehydrohalogentation? C-D bond stronger than C-H bond.

13 Isotope Effect NaOEt NaOEt kH/kD = 7

14 Isotope effect shows that C-H bond broken in the transition state.

15 Element Effect Change Element I > Br > Cl

16 SYN vs. ANTI Elimination
Same Side Opposite Side

17

18

19 Transition State Energy Starting Material Product

20 E 2 2 Bonds at a time Elimination

21 Procedure

22 Put cyclohexanol and sulfuric acid in round bottom flask
Fractional Distillation (steam distillation) collect distillate 80-85o Dry product with K2CO3 4. Distill

23 Distil immiscible liquids
PT = PA PB (Steam Distillation)

24 Baeyer Unsaturation Tests
Potassium Permanganate KMnO4

25

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27 Bromine and Cyclohexene

28


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